Title

Author

Date of Defense

Spring 4-22-1998

Department

Biological Sciences

First Advisor

Susan Stapleton, Chemistry

Second Advisor

John Spitsbergen, Biological Sciences

Third Advisor

David Reinhold, Biological Sciences

Abstract

In recent years, interest has surfaced in the use of insulin-mimicking agents for diabetic therapies. Zinc has been shown to have insulin-like effects in vivo and in vitro but has never been studied for its ability to mimic insulin in the regulation of carbohydrate and fatty acid metabolism. Therefore, the author studied the effects of zinc on glucose-6-phosphate dehydrogenase (G6PDH), an enzyme stimulated by insulin that is imperative in both carbohydrate and fatty acid metabolism. Because G6PDH is highly regulated in liver cells, a stable rat liver cell line, Buffalo Rat Liver (BRL), was used. Endogenous G6PDH activity and G6PDH promoter activity were both significantly stimulated at 1 µM [Zn2+]. Two antioxidants, trolox C and catalase, eliminated the zinc-induced increase of endogenous G6PDH activity and G6PDH promoter activity respectively. Further studies were performed to investigate whether zinc effects are produced due to the generation of reactive oxygen species. Upon addition of trolox C and zinc, BRL cell death was decreased compared to the zinc alone treatment. A compound known to eliminate glutathione, BSO, had no effect on BRL cell viability. These results infer that the mechanism of zinc action does involve the generation of reactive oxygen species (ROS) but that zinc does not produce ROS through the depletion of glutathione. Zinc has also been shown here to be toxic only at very high concentrations, a phenomenon seen with vanadate and selenate, two well-studied insulin mimetics. The results presented here demonstrate that zinc regulates G6PDH similarly to insulin and generate enthusiasm for zinc as a possible insulin mimetic.